Control device



Jan. 24, 1967 P. HERMANNS 3,300,151

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 1 Fig.2

180 ANBLEO PRUGRESSIVELY BETTING SMALLER APPRUXIMATION OF THE CURE TUFIELD SHUNT POSITION INVENTOR: PETER HERMANNS BY /6ruw-wc 5 42 vATTORNEYS Jan. 24, 1967 P. HERMANNS 3,300,161

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 2 INVENTOR: PETERHERMANNS BY A Jw/WL ATTORNEYS Jan. 24, 1967 P. HERMANNS 3,300,161

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 5 INVENTOR:

PETER HERMANHS y A mot c 4 ATTORNEYS a Jan. 24,

Filed Sept. 21, 1964 P. H ERMANNS CONTROL DEVICE 4 Sheets-Sheet 4INVENTOR= PETER HERMAHNS BY 6,6114% g A! ATTORNEY Patented Jan. 24, 19673,300,161 CONTROL DEVICE Peter Hermanns, Cologne, Germany, assignor toFrau Sigrid Heim nee Krukenberg, Cologne-Zollstock, Germany Filed Sept.21, 1964, Ser. No. 398,001 Claims priority, application Germany, Sept.21, 1963, H 50,326; Mar. 20, 1964, H 52,108 Claims. (Cl. 242154) Thepresent invention relates to an electrical control arrangement forthread or yarn tension devices of textile machines, particularlyspooling or winding machines, wherein the yarn passes between two guideelements which are movable relative to each other and tension the yarnby braking it.

As is known, the yarn is kept under a certain tension by means of atensioning device or yarn brake during a spooling process. Particularlywhen winding synthetic fibers, it is important that a uniform orotherwise predetermined yarn tension be achieved at the yarn. Alengthwise deformation of the yarn because of too high a take-uptension, as well as tension fluctuations which are too large during thespooling process are very much dreaded, since such yarns which are notwound with a uniform or fixedly predetermined yarn tension lead perforceto rejects during the subsequent processing when the yarn is knitted,etc.

Various apparatus have already been known in order to regulate the yarntension during the processing on textile machines, or to keep the yarntension at a predetermined value. In these known yarn tension regulatingdevices, lattice or grid braking, disk braking, friction braking, orsimilar braking systems are utilized which provide the yarn with thedesired tension during its path through the redrawing or processingsteps, the yarn it self being more or less braked and thus put undertension by variable friction when passing the braking system. Thefactors determining the yarn pull and thus the friction within thebraking system are automatically controlled in dependence upon the yarntension so that a yarn tension difference with respect to a preselectednormal yarn tension, which may occur at times, and which arises from thefeed, is automatically compensated for.

Sensing and thus a measuring or control of the yarn tension present at aparticular time is thus the starting point for all control andregulating processes. These control and regulating processes are carriedout electrically, so that an electrical value is provided by the sensingsystem as the tension setting value.

In order to transfer the mechanical value of the yarn tension uponelectrical elements, generally at first the pulling force or elasticforce directly derived from the yarn tension is compared with an elasticforce effective oppositely thereto. For this purpose, sensing fingers ormovable yarn guide eyes are normally provided which are pretensioned bymeans of spring forces or magnetic forces and which counteract the yarntension. It is also possible to provide guide pins or rollers whichtransmit a motion dependent upon the yarn pull to the electric elementsin various manners. In order to provide as smooth a translation of themechanical adjusting value into an electrical adjustment value aspossible, there have already been proposed bridge bolometers,photoelectric as well as capacitive or also inductive devices, or alsolow-friction adjustable resistors or potentiometers.

With these features of the prior art in mind, it is a main object of thepresent invention to provide an electromagnetic yarn tension sensing andregulating device for thread braking systems which is endowed withspecial advantages and improvements as compared to known devices.

Another object of the invention is to provide a yarn sensing devicewhich is constructed so that a control and regulating can be used withit which does not require compensation circuits in the regulatingcircuitry.

These objects and others ancillary thereto are accomplished inaccordance with preferred embodiments of the invention wherein controldevice is provided with three guide elements which are arranged to forma triangle so that the yarn passed therethrough forms a so-called yarntriangle. At least one yarn guide element, pref erably the guide elementin the center, is mounted to be movable at right angles to the path ofthe yarn. On account of the yarn passing around the yarn guide elementsalong a triangular path, there arises a force component from the pullingforce effective at the yarn in the direction 'of travel. This componentis effective at right angles to the path of the yarn and exerts anadjustment moment upon the movable yarn guide element, so that theforces becoming effective through the yarn tension tend to straightenout the triangle and to bring the yarn into a straight line.

According to the invention, an electromagnetic pulling force iseffective upon the movable yarn guide element of the triangle, whichforce is opposite to the partial component derived from the yarn tensionin the direction of motion at right angles to the path of the yarn.

If both forcesthe magnetic pulling force and the component from the yarntensionare of the same magnitude, the system assumes a rest position. Ifone of the two forces predominates, there is a momentary shift into theone or the other direction, until the force relationship is balanced.With the shift of the movable yarn guide element there is connected theshifting of an electrical element in order to deliver a setting oradjustment value for an electrical yarn brake or tensioning device.

Additional objects and advantages of the present invention will becomeapparent upon consideration of the following description when taken inconjunction with the accompanying drawings in which:

FIGURE 1 is a schematic view of a yarn triangle device.

FIGURE 2 is a graph showing the relationship of yarn angle to acomponent of the yarn pulling force.

FIGURE 3 is a schematic view of a yarn triangle device using anelectromagnetic device and a photoelectric device.

FIGURE 4 is a graph showing the relationship of the force of magneticattraction or magnetic pulling force to the position of the core withrespect to the coil.

FIGURE 5 is a graph showing the curves of FIGURES 2 and 4 plotted on thesame scale.

FIGURE 6 is a side elevational view, partly in section, of a winder.

FIGURE 7 is a front elevational view of the yarn sensing device.

FIGURE 8 is a plan view of the yarn sensing device of FIGURE 7.

FIGURE 9 is a front elevational view of the yarn braking or tensioningdevice.

FIGURE 10 is a circuit diagram of the control for the yarn tensioningdevice.

FIGURE 11 is a circuit diagram of a simplified potentiometer-typearrangement for varying the yarn tension.

FIGURE 12 is a circuit diagram similar to FIGURE 11 but arranged todegressively decrease yarn tension with increasing spool diameter.

FIGURE 13 is a schematic view of a yarn triangle device using acondenser instead of a photoelectric device.

FIGURE 14 is a schematic view of a yarn triangle device using a variableinductor.

FIGURE 15 is a schematic view of a plurality of coils 3 in electriccircuits which are commonly controlled by a control device.

Before considering the drawings in detail, the sequence of the controlsteps of a known device will be considered.

The starting point of this consideration is to be an equilibrium of theentire control and tension system, with an assumed yarn tension of thevalue X. Yarn tension and electromagnetic force are equal, so that theyarn sensing system remains at rest in a certain position. Theelectrical element coupled with the momentary position of the movableyarn guide element delivers in this setting a certain electrical valueto the yarn tensioning device, as the setting value. This setting valuecauses a setting of the tension device so that a yarn tension of theassumed value X is reached.

Furthermore, it is assumed that now from time to time a yarn tensiondifference having the value Y occurs, caused by the feed. This yarntension difference of the magnitude Y which follows the state ofequilibrium with the yarn tension having a value X, causes a shift ofthe movable yarn guide element against the fixedly set electromagneticforce. With this shift, there is also connected the shifting of theelectrical element so that now a setting value is delivered to thetension system which is capable of adjusting the tension system suchthat a compensation of the yarn tension difference, which has occurredfor a time, is carried out.

With progressive compensation of this assumed yarn tension difference,the yarn tension naturally approaches again the initial value, i.e., thevalue X. With the ap pr-oach of the yarn tension to the starting value,however, there is perforce connected an adjustment of the movable yarnguide element and, with it, of the electrical element, to the startingpoint of the regulating processes. However, in this starting position, asetting value is delivered to the tension or bracking system by theelectrical element which value corresponds to the normal feed tension ofthe yarn. If the interference which causes the yarn tension differencehaving the value Y continues, the yarn tension difference having thisvalue occurs again and the abovedescribed process is repeated. Thesetting value necessary for completely covering the yarn tensiondifference Y is consequently always lost with progressive compensationof the temporarily occurring yarn tension and after every completedcompensation, a setting value is delivered by the electrical element,which value corresponds to the yarn tension difference which is stillpresent.

It can thus be seen that the setting value which is delivered by theelectrical element to the brake system is consequently subject tovariations during the entire duration of the yarn tension differencehaving the value Y. Therefore the setting value varies between the valuewhich corresponds to the normal feed tension having the value X in thestarting position and the value which corresponds to the occurring yarntension difference Y. In practice, only a compensation of about 50% ofthe difference occurring from time to time is possible with such acontrol or regulating apparatus.

In order to compensate completely for a yarn tension difference, asubstantially more complicated regulating circuit is required. It isnecessary, in this connection, to carry out a compensation within theentire regulating circuit, perhaps such that a second yarn tensionsensing device is inserted between feed and tension system which yieldsa compensation tension which strengthens or weakens the electromagneticfield of the first yarn tension sensing device in accordance withincreasing or decreasing feed tension, so that the setting value presentwhen the yarn tension difference with respect to the predeterminedactual value occurs at the first moment of the regulating processes ismaintained. There are still other ways possible to derive electricalcompensation values from the entire regulating circuit for example fromthe relative position of the tension system, and to feed these valuesinto the regulating circuit in such a manner that a complete yarntension regulation is made possible. Such regulating circuits areextraordinarily complicated and expensive, and it is dilficult tomaintain the necessary regulating characteristics across the requiredrange.

In contradistinction thereto, the device according to the inventionmakes possible a complete compensation of an occasionally occurring yarntension difference, Without an additional application of a compensationvalue being necessary.

The force component arising in the yarn triangle at right angles to thedirection of motion of the yarn is, in addition to being dependent onthe pull tension at the yarn in the direction of motion, dependent uponthe relative position of the three yarn guide elements with respect toone another, i.e., with increasing yarn angle within the yarn guideelements of the yarn sensing device, the component which is effective atthe central yarn guide element at right angles to the path of the yarnbecomes smaller.

With more particular reference to the drawings, FIG- URE 1 schematicallyshows a yarn triangle device. Yarn 10 passes through the yarn guideelements 11, 12', and 13 arranged in a triangle with respect to oneanother, and forms an angle a. The yarn 10 extends in the direction ofmotion indicated, the force K becoming effective as a pulling force. Inthis position of the yarn guide elements with respect to one another, aforce component K is effective at the central yarn guide element 12,this force extending in the direction indicated. When the central yarnguide element is shifted into the position shown in dashed lines, theangle at becomes larger, as can be seen from FIGURE 1. The component K,however, is smaller in this position, the pulling force K at the yarn inthe direction of motion being the same.

FIGURE 2 shows schematically in a graph the relationship between thecomponent K and the yarn angle oz. The graph shows that, at the yarnangle of the component K is practically zero, and that the componentincreases, with decreasing yarn angle, approximately according to thecurve as illustrated.

According to the invention, at least one of the yarn guide elementsarranged in a triangle is mounted to be movable at right angles to thepath of the yarn and is under electromagnetic pulling force in thedirection of motion.

FIGURE 3 shows an embodiment of such an arrangement wherein the centralyarn guide element is movably mounted. The yarn 10 is guided along theyarn guide elements 11, 12 and 13. The movable yarn guide element 13 isconnected with the magnetic core 14 which moves into the field of a coil15. At the connecting member 16 which connects the movable yarn guideelement 12 with the magnetic core 14, there is connected a light vane 17which covers a photoelectric cell 18 partially on the active layeragainst light in a direction at a right angle to the plane of thedrawing.

If the magnetic coil 15 is energized with a current, the magnetic fieldexerts a certain force upon the armature 14, this force being dependent,if the passage of current is constant, substantially upon the relativeposition of the core 14 with respect to the field of coil 15. Theattractive force becomes progressively greater during the approach ofthe armature into the so-called field shunt position and becomes smallerwhen the armature moves progressively farther away from the field of thecoil.

FIGURE 4 shows, graphically, the relationship between the relativeposition of the core with respect to the magnetic coil and the force ofmagnetic attraction or pulling force P resulting therefrom. The graphshows that the force P increases in accordance with the course of thecurve illustrated and assumes its highest value in the field shuntposition.

The essential feature of the invention is that the two oppositelyeffective forces from the yarn triangle and from the electromagneticfield are balanced with respect to each other by suitable geometric andmechanical adjustment of the yarn triangle to the dimensioning andarrangement of the electrical magnitude of the electromagnetic field,and by suitable choice of the characteristic of the path-field strengthrelationship. This balancing is done such that the curve paths of thetwo forces according to FIGURES 2 and 4, as shown in FIGURE 5, aresubstantially congruent along a portion of their path. If the twoopposite forces along this portion of the curve of the diagram accordingto FIGURE 5 are effective between the points a and b, there is acomplete force equilibrium and the sensing device is in a rest position.Within the region between points a and b, the component from the yarntension decreases or increases, when the movable yarn guide element isshifted, to the same extent to which the oppositely effective magneticforce also decreases or increases, this force arising from theconcomitant, equally large shift of the magnetic armature with respectto the magnetic field of the coil.

With such a yarn sensing device constructed according to the invention,a control and regulating device for yarn tension devices can be operatedwithout complicated regulating circuits with compensaton circuits beingnecessary.

Similar to the consideration of the regulating processes in theforegoing description, there shall again be considered an equilibrium ofthe entire regulating system as the starting point, with an assumed yarntension of the magnitude X. Yarn tension and electromagnetic force arethe same so that the yarn sensing system remains at rest in a certainposition. The light vane 17 covers the photoelectric element 18 to acertain extent, so that a setting value is delivered from this elementto a subsequent amplifier circuit. This setting value exerts such aninfluence upon the yarn tension device which is connected to theamplifier output, that the tension device assumes a setting whichresults in a yarn tension of the assumed magnitude X.

Furthermore, it is assumed that now an occasional yarn tensiondifference of the magnitude Y occurs which is caused by the feed. Thisyarn tension difference of the magnitude Y, following the equilibriumcondition having the yarn tension of the magnitude X, causes a shift ofthe equilibrium and thus a shift of the movable yarn guide element. Withthis shift, there is also a corresponding shift of the light vane 17, sothat the photoelectric element receives a different amount of light andthus a correspondingly different setting value is delivered to thetensioning system via the amplifiers. This setting value adjusts thetension system such that a compensation of the occasional yarn tensiondifference is carried out. With the progressive compensation of thisassumed yarn tension difference by means of the progressive change inthe braking action, the yarn tension naturally again approaches thestarting value, namely the value X.

On account of the occurrence of the yarn tension difference, the movableyarn guide element and with it the magnetic core were shifted as theequilibrium of the forces was disturbed. When the yarn tensiondifference is completely compensated for, there is again an equilibriumin the described arrangement between the force component from the yarntriangle device and the oppositely effective force from theelectromagnetic system, although the basic setting has changed withrespect to the initial setting, because, with the same pulling force atthe yarn along a certain adjustment range of the sensing device, theequilibrium is maintained, as can be seen from the above explanations inconnection with FIGURE 5. The light vane 17 thus has kept its settingwhich it assumed when the yarn tension difference occurred, this beingdifferent from the starting position of the operation, and the settingvalue which is now delivered by the photoelectric element fullycompensates for the difference value which has occurred, so that withthe device according to the invention a complete compensation of theoccasionally occurring yarn tension difference is possible, without acomplicated regulating circuit with restoration and compensation beingnecessary.

If, after these regulating processes have been completed, a furtherdisturbing magnitude arises anew, for example a yarn tension differencein the opposite direction, there is momentarily again a shift of themovable yarn guide element and thus of the light vane. Thus, a changedsetting value is delivered, and by adjusting the tensioning system, acompensation of the yarn tension difference is carried out. The yarnsensing system now assumes a different position, but at the moment ofadjustment of the yarn tension to the starting point, there is againcomplete equilibrium.

By using a photodiode as the photoelectric element and by using atransistorized amplifier, connected thereafter, for the amplification ofthe setting value-and as described in more detail hereinaftersuch anamplification can be achieved that the relative total shift of themovable yarn guide element and the magnetic core can be limited inpractice to fractions of a millimeter. By this means, very shortadjustment paths and adjustment periods of the yarn sensing device canbe obtained.

According to a further development of the invention, the flow of currentthrough the winding 15 of the magnetic coil is controlled by means of apotentiometer-like circuit. The electoromagnetic basic setting is variedand the fixed output of a desired value for the desired yarn tension ismade possible. This desired value is read either from a calibratedpotentiometer or from an indicating device.

In the textile industry, it is almost always necessary to have a ratherlarge number of winding machines in order to produce larger quantitiesof spools, cones, cheeses, quills, etc., at the same time. Greatestimportance is given to the achievement of as uniform a yarn tension onall spools as possible. For obtaining this uniformity, a. greatexpenditure in operating personnel for the machines is required atpresent.

According to a further feature of the invention, as many yarn sensingsystems as desired are combined electrically and are supplied withmagnetizing current through a control circuit, for example by means of acontrol desk. In this manner, a central regulation of the amount of theyarn tension can be carried out. The choice of the magnitude of the yarntension can be dependent upon the type of the yarn used.

For various reasons inherent on the one hand in the homogeneousconstruction of the spool itself and on the other hand in the technicalrequirements of the textile art during the further processing of thespools manufactured on the spooling machines, a degressive decrease ofthe yarn tension is desired with increasing spool diameter.

A further component of the inventive idea is thatthe electromagneticfield of the yarn sensing device is controlled in a second circuit or ina more detailed circuit of the first type which has been described abovesuch that the flow of current through the winding of the magnetic coil15 is influenced by a second potentiometer which is set in dependenceupon the diameter of the take-up spool, for example, in dependence uponthe position of the yarn guide flap. Thus, it is possible to achieveautomatically, either step-wise or continuously, a yarn tension whichdecreases, for example, degressively.

By means of the inventive device, any type of control or regulation ofthe yarn tension can be carried out, i.e., not only the change of thebraking effect by means of a yarn brake known per se with meshing guideelements or by changing the braking action of disc brakes, but it isalso possible to influence an acceleration of the yarn passage.

The translation of the mechanical shifting movement of the yarn sensingsystem when a yarn tension difference occurs with respect to thepreselected normal value, into an electrical setting value can becarried out in the most varied manner.

The photoelectric device shown in FIGURE 3 is only shown as an examplefor a device according to the invention. The movable yarn guide elementcan also be coupled with a capacitance, or inductance, or apotentiometer, or other electrical signal producing systems whosechanges then serve as control basis for the regulating device of theyarn brake.

An embodiment of a control and regulating device constructed accordingto the invention for a yarn brake will now be described, together withthe tensioning device itself and the electric circuit pertainingthereto.

FIGURE 6 shows the path of the yarn 10, from a bobbin or other yarnsupply 20 via an electromagnetic tensioning system 21, yarn sensingsystem 22 to a take-up spool 23. From this figure, also the basicconstruction of the entire winding machine with drive motor andpivotable yarn guide can be seen.

As can be seen from FIGURE 7, the yarn triangle device which has beenexplained in detail in the foregoing is formed between the yarn guidepins 11 and 13 and the yarn sensing element. FIGURES 7 and 8 furthermoreshow the position of the magnetic coil 15, as well as the position ofthe light vane 17 arranged on a member 16b, which member also has theiron core 14 which moves into the magnetic coil I secured thereto. Theconnecting member 16 passes through the member 16b and has the yarnsensing member 12 arranged at the end thereof.

This light vane controls, depending upon the size of the yarn triangle,the amount of light from the light source 24 which reaches thephotoelectric cell 18.

In the embodiment of a yarn sensing device shown in FIGURES 7 and 8, theyarn sensing element 12 is rotatably mounted with the stucture 16 at oneend and thus is pivotable into a vertical line so that various anglescan form within the yarn triangle during the operation of the device. Inorder that short tugs at the yarn cannot become effective and so thatthe control device is protected against undesired natural oscillationprocesses, hydraulic damping is provided. For this purpose, a vane 16ais provided which is connected to member 16. This vane operates as adamping element in a chamber which is filled with damping oil. Thecontainer is sealed against the pivotable connecting member 16 by meansof a collar. The movement of the yarn sensing member 12 causes themember 16 to pivot which motion is then transferred to the member 16bresulting in a movement of the light vane 17 and the core 14 which aresecured to the member. this light vane is adjusted with respect to thelight source 24- and the photoelectric cell 18 such that during a motionthe light beam is covered more or less, so that the photocell, incorrespondence with the lighting, controls the amplifier connectedthereafter to a greater or lesser degree.

The construction of the yarn tensioning system 21 (cf. FIGURE 6) whichsystem is controlled by the yarn sensing system via an amplifier, isshown in FIGURE 9. The yarn is pulled through the tensioning gridcomprising the stationary braking lattice 25 and the movable brakinglattice 25a. The movable braking lattice 25a is fastened at the magneticarmature 26 so that the magnet armature is pulled into the coil whencurrent is flowing through winding 27 and the braking lattice becomesnarrower, and thus a larger friction is transmitted to the yarn. Inorder that the magnet armature 26 can operate without any frictionalengagement with the interior of the winding or other components, thisarmature is fastened to supports 28 extending in the front and/ or inthe rear, in transverse direction. These supports are fashioned as leafsprings and thus permit a shifting of the armature 26 in the axialdirection. The magnet armature 26 is connected, via connection member29, with a hydraulic damping device 30 which exerts such a damping uponthe shifting of armature 26 that an overshooting of the displacementinitiated by the yarn sensing device via the amplifier is avoided.

FIGURE 10 is a circuit diagram of the required control amplifier whichis electrically connected to the output of the yarn sensing system andcorrespondingly amplifies the setting value delivered by the lattersystem. The amplifier feeds this setting value to the tensioning system.

The amplifier is fed with a preferably stabilized direct current voltageat inputs 31. This voltage arrives, via a suitable resistor, at the lamp24 which controls the photoelectric cell 18. The quantity of light iscontrolled, as set forth above, by the respective position of the lightvane 17. The photoelectric cell 18 lies in series with the voltagedivider resistors 32, 33 and 34. The base of transistor 35 is connectedbetween the divider resistors 32 and 33.

The voltage potential between the resistors 32 and 33 varies independence upon the lighting condition of the photoelectric cell 18, sothat the base of the transistor 35 which is there connected is likewisemore or less controlled in dependence upon the lighting condition of thephotoelectric cell. If transistor 35 becomes more or less conductive onaccount of a change in the base voltage at transistor 35, a variedpotential likewise appears, at the divider resistors 37 and 36, so thatthe transistor 38, in correspondence with the amplification factor oftransistor 35 is likewise controlled to a greater or lesser degree. Thewinding of the tensioning magnet 27 lies in the output circuit of thetransistor. This tensioning magnet 27 shifts the movable braking lattice25a in correspondence with the passage of current set by transistor 38.Resistor 39 controls the minimal flow of current through the tensioningmagnet, with transistor 38 being blocked, so that a certain setting ofthe braking lattice is maintained. Because of this, it is possible bymeans of the braking system, to generate a minimal yarn tension at thestart of the machine before the yarn tension regulation has begun andthus the start of a proper winding operation is made possible. With thebeginning of the regulating operation, the transistor 38 takes over thecontrol of the flow of current through the winding of magnet 27.

A capacitor 40 in series with a variable resistor 41 is connected inparallel with the resistor 34 and the photoelectric cell. Thereby thevoltage potential at the photoelectric cell has a time constant whichcan be changed by the variable resistor in accordance with requirements.This manner of connection serves for damping and prevents the occurrenceof control oscillations.

The mode of operation of the device has already been explained in detailin the first part of this description. The yarn It) forms the yarntriangle between the yarn guide elements 11, 12 and 13 (cf. FIGURES 1, 3and 7). A pulling force is effective at the central yarn guide element12, which force is opposite to the force of the electromagnet 15.

Analogously to the explanation of the first portion of the description,the two oppositely effective forces are balanced or adjusted to eachother by means of suitable geometric and mechanical adjustment of theyarn triangle to the path-field strength relationship of theelectromagnetic device 14, 15 operating in a middle region of thepath-field strength curve (cf. FIGURES 4 and 5), such that a completeequilibrium of the forces is maintained across a required adjustingrange of the yarn sensing element 12.

If this equilibrium is disturbed by the occurrence of a difference inyarn tension, a shift of the sensing element 12 takes place. With thisshift, there is a change in lighting of the photoelectric cell 18. Thiscell effects a change of the amplification of the amplifier (cf. FIGURE10) so that the tensioning device 21 is actuated correspondingly. Afterthe yarn tension difference which occurred is compensated for by avaried setting of the tensioning system 21, the yarn sensing device andthus the entire regulating device is again in a state of equilibrium.

The flow of current through the electromagnet 15 and therefore itsmagnetic force, Within the yarn sensing systern 21, is important for themaintaining of a certain value of the yarn te sion. FIGURE 11 shows asimplified circuit diagram for setting a predetermined yarn tension. Forthis purpose, an electrical control desk 42 pertaining to the machine isprovided. This control desk transforms the main voltage fed thereto intoa direct current voltage of, for example, 24 volts. A potentiometer 43with the slide 44 lies in the output of the control desk forpreselecting the yarn tension. It can be seen that the potentiometer 43is eflective as a voltage divider and that the electromagnet 15 receivesa greater or lesser voltage, depending upon the setting of slide 44.Thus, the armature of the magnet 15 is pulled into the coil to a greateror lesser degree and the yarn triangle assumes a changed basic positionso that the desired value for the desired yarn tension is provided. Anindication of the preselected yarn tension can be obtained either byinserting a voltmeter in parallel with the electromagnet 15 or bytransmitting the respective position of the slide 44 to a calibratedscale.

FIGURE 12 shows a circuit diagram similar to FIG- URE 11 for theautomatic control of yarn tension which is varied with increasingwinding diameter and which decreases degressively, for example.According to this circuit diagram, the slide 44 of the potentiometer 43operates in conjunction with a subsequent potentiometer 45 with theslide 46. This potentiometer is located within the machine, as can beseen from FIGURE 6.

On the axis of rotation 47 of the pivotable yarn guide flap 48, atoothed gear 49 is positioned which mes-hes with a pinion 50. Thispinion is seated on the axis of the potentiometer 45. If the diameter ofthe winding spool 23 is increased, the arm of the yarn guide flap ispivoted and is shifted, via the cogwheels 49 and 50 of the slide 46 (cf.FIGURE 12) of the potentiometer 45, in such a manner that a lowervoltage occurs at the output of the potentiometer. With decreasingvoltage at electromagnet 15, a lower yarn tension is achieved.

Thus, it can be seen that a decreasing yarn tension can be obtained withthe circuit of FIGURE 12 which is automatically controlled by theincreasing diameter of the spool during the re-spooling process.

Instead of the photoelectric device, parts 18, 17, one can useas thecase may bea variable condenser 18a, FIGURE 13, or a variable inductor18b, FIGURE 14.

The common control device, FIGURE 15, comprises, on principle, thecommon potentiometer 43 of desk 42. However, a multiple structure ofpotentiometers 45 and slides 46 will be necessary as shown for a set ofcoils 15.

It will be understood that the above description of the presentinvention is susceptible to various modifications,

changes and adaptations, and the same are intended to be comprehendedwithin the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A yarn tensioning device for textile machines comprising incombination: yarn guide means including a plurality of elements arrangedto form a triangle and through which yarn passes, one of said elementsbeing movable in a direction at right angles to the yarn path to bemoved by a component of yarn pull in said direction so that there is afirst force on said movable element in said direction; electromagneticmeans connected to said movable element for providing a second forceopposite to said first force; the curve of the path-pulling forcerelationship of said electromagnetic means being balanced with the curveof the path-pulling force relationship of the yarn guide means so thatthe two curves and thus the oppositely effective forces are congruentalong a certain minimum path of the adjusting region of the device andan equilibrium of the forces is maintained at positions along thisregion with the yarn pull remaining the same; electrical means coupledwith said movable yarn guide element so that when said movable elementmoves, a proportional change of an electrical value of said electricalmeans takes place; a yarn tensioning assembly; and an electrical circuitconnected to control said assembly and connected to receive a signalfrom said electrical means which is significant of the change of theelectrical value and which is a setting value for said assembly.

2. A device as defined in claim 1 wherein said electrical means includesa photoelectrical element and a light vane connected With said movableelement.

3. A device as defined in claim 2 wherein said photoelectrical elementis a photodiode.

4. A device as defined in claim 1 wherein said electrical means includesa capacitor whose capacitance varies with the movement of said movableelement.

5. A device as defined in claim 1 wherein said electrical means includesan inductance circuit whose inductance varies with the movement of saidmovable element.

6. A device as defined in claim 1 wherein said electromagnetic meansincludes a winding and a circuit including a potentiometer forcontrolling the current in said winding for setting a predetermined yarntension.

7. In combination, a plurality of yarn tensioning devices as defined inclaim 1 wherein each of said electromagnetic means is provided with awinding, and further comprising an electric circuit into which saidwindings are combined for centrally controlling said windings andincluding a potentiometer, so that the flow of current through saidwindings may be controlled.

8. A device as defined in claim 1 comprising spool means onto which theyarn is to be Wound, and potentiometer means connected to sense theincreasing diameter of said spool means and to control current in saidelectromagnetic means to decrease yarn tension with increasing spoolmeans diameter.

9. A device as defined in claim 8 wherein said potentiometer meansincludes a rotatable potentiometer controlled by a yarn guide flap whichpivots with increasing spool means diameter.

10. A device as defined in claim 9 wherein said rotatable potentiometerincludes a pinion and said yarn guide flap includes a cogwheel meshingwith said pinion whereby pivoting of said flap rotates saidpotentiometer.

References Cited by the Examiner UNITED STATES PATENTS 2,754,071 7/1956Furst et a1 242--l 54 3,146,968 9/1964 Band 242-149 FOREIGN PATENTS1,200,676 6/1959 France.

225,541 5/ 1943 Switzerland.

STANLEY N. GILREATH, Primary Examiner.

1. A YARN TENSIONING DEVICE FOR TEXTILE MACHINES COMPRISING IN COMBINATION: YARN GUIDE MEANS INCLUDING A PLURALITY OF ELEMENTS ARRANGED TO FORM A TRIANGLE AND THROUGH WHICH YARN PASSES, ONE OF SAID ELEMENTS BEING MOVABLE IN A DIRECTION AT RIGHT ANGLES TO THE YARN PATH TO BE MOVED BY A COMPONENT OF YARN PULL IN SAID DIRECTION SO THAT THERE IS A FIRST FORCE ON SAID MOVABLE ELEMENT IN SAID DIRECTION; ELECTROMAGNETIC MEANS CONNECTED TO SAID MOVABLE ELEMENT FOR PROVIDING A SECOND FORCE OPPOSITE TO SAID FIRST FORCE; THE CURVE OF THE PATH-PULLING FORCE RELATIONSHIP OF SAID ELECTROMAGNETIC MEANS BEING BALANCED WITH THE CURVE OF THE PATH-PULLING FORCE RELATIONSHIP OF THE YARN GUIDE MEANS SO THAT THE TWO CURVES AND THUS THE OPPOSITELY EFFECTIVE FORCES ARE CONGRUENT ALONG A CERTAIN MINIMUM PATH OF THE ADJUSTING REGION OF THE DEVICE AND AN EQUILIBRIUM OF THE FORCES IS MAINTAINED AT POSITIONS ALONG THIS REGION WITH THE YARN PULL REMAINING THE SAME; ELECTRICAL MEANS COUPLED WITH SAID MOVABLE YARN GUIDE ELEMENT SO THAT WHEN SAID MOVABLE ELEMENT MOVES, A PROPORTIONAL CHANGE OF AN ELECTRICAL VALUE OF SAID ELECTRICAL MEANS TAKES PLACE; A YARN TENSIONING ASSEMBLY; AND AN ELECTRICAL CIRCUIT CONNECTED TO CONTROL SAID ASSEMBLY AND CONNECTED TO RECEIVE A SIGNAL FROM SAID ELECTRICAL MEANS WHICH IS SIGNIFICANT OF THE CHANGE OF THE ELECTRICAL VALUE AND WHICH IS A SETTING VALUE FOR SAID ASSEMBLY. 